JPS62193641A - Production of microcapsule - Google Patents

Abstract

PURPOSE:To efficiently produce the titled microcapsule by emulsifying a hydrophobic liq. contg. a polyvalent isocyanate in the hydrophilic soln. of a specified polyvinyl alcohol to form a synthetic polymeric substance at the interface between the liq. droplets. CONSTITUTION:A polyvinyl alcohol having 0.5-0.8 iodine absorbance is prepared. In this case, 7ml of water is added to 1ml of 0.5% aq. soln. of the polyvinyl alcohol, 2ml of 0.001N aq. iodine soln. (in the 1/2 weight ratio of iodine to potassium iodide( is further added dropwise, the mixture is agitated for 20min to obtain a soln., and the absorbance is measured by using the soln. at 480mmu. The hydrophobic liq. contg. a polyvalent isocyanate is emulsified in the hydrophilic soln. of the polyvinyl alcohol, and a synthetic polymeric membrane is formed at the interface between the liq. droplets to produce the microcapsule covering the surface of the liq. droplet. From 0.5-20pts.wt. polyvinyl alcohol is appropriately dissolved in 100pts.wt. hydrophobic liq.

Description

Detailed Description of the Invention "Industrial Application Field" 11 The present invention relates to a method for producing microcapsules containing a hydrophobic core material, and in particular, microcapsules formed by the reaction of a polyvalent isocyanate and a compound having active hydrogen. The present invention relates to a method for industrially and extremely efficiently manufacturing microcapsules having a synthetic polymer membrane.

"Prior Art" Various methods are known for producing microcapsules, such as coacervation, interfacial polymerization, and 1n-situ polymerization, but the encapsulation method of the present invention is particularly suitable for interfacial polymerization. This is related to the improvement of

The interfacial polymerization method is an encapsulation method in which a synthetic polymer wall film such as polyurea or polyurethane is formed at the interface between a hydrophobic liquid and a hydrophilic liquid. A method for obtaining capsules having a polyurea wall film by reacting with water or amines is described, and Japanese Patent Publication No. 4'l-43740, Japanese Patent Publication No. 1350-a of 1983, etc. disclose hydrophilic capsules containing polyvinyl alcohol. A method for obtaining capsules by reacting polyvalent isocyanates in a neutral liquid is described.

Usually, in the interfacial polymerization method, an aqueous solution of an emulsion stabilizer is used as the hydrophilic liquid in order to efficiently emulsify and disperse a hydrophobic liquid containing a polyvalent isocyanate in a hydrophilic liquid. Examples of such emulsion stabilizers include polyvinyl alcohol, anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, gelatin, gum arabic, carboxymethylcellulose, polyacrylamide, hydroxyethylcellulose, methylcellulose,
Ethylcellulose, cellulose acetobutyrate, hydroxymethylcellulose, polyvinylpyrrolidone, montmorillonite, lignin sulfonic acid, polystyrene sulfonic acid and its copolymers, hydrolysates of maleic anhydride copolymers, polyacrylic acid and its copolymers, poly Examples include methacrylic acid and copolymers thereof, polyacrylamidomethylpropanesulfonic acid and copolymers thereof, and salts thereof, and these emulsion stabilizers may be used alone or in combination.

Among them, polyvinyl alcohol is preferably used because it has high emulsifying ability and is inexpensive, and contributes to the production of microcapsules with excellent heat resistance, moisture resistance, light resistance, etc.

"Problems to be Solved by the Invention" However, polyvinyl alcohol, which has been used in this way, has the following problems, and therefore improvements are desired.

That is, when ordinary polyvinyl alcohol is dissolved in water, it tends to generate bubbles and tends to form lumps.

Therefore, bubbles are likely to be generated during the reaction to form the capsule wall membrane, and it is necessary to adjust the stirring of the capsule manufacturing system. However, if the stirring is insufficient, deposits will form on the walls of the reaction vessel, so when implementing it on an industrial scale,
This has become a big problem.

Therefore, the object of the present invention is to solve the above-mentioned problems associated with polyvinyl alcohol in an interfacial polymerization method in which a hydrophobic liquid containing a polyvalent isocyanate is emulsified and dispersed in a hydrophilic liquid containing polyvinyl alcohol to form a capsule. The object of the present invention is to provide a method for industrially and efficiently producing microcapsules having excellent properties.

"Means for Solving the Problem" The present invention emulsifies and disperses a hydrophobic liquid containing a polyvalent isocyanate in a hydrophilic liquid containing polyvinyl alcohol to form a synthetic polymer film at the droplet interface. The method for producing microcapsules that envelops the surface of the droplet is characterized in that polyvinyl alcohol having an iodine absorbance of 0.5 to 0°8 as defined below is used as the polyvinyl alcohol. It is.

(Iodine absorbance) 1 ml of 0.5% polyvinyl alcohol aqueous solution + 7 ml of water
ml, 2 ml of a 0.0 OIN iodine aqueous solution (iodine:potash iodo/1:2 weight ratio) was added dropwise and stirred, and the absorbance of the solution was measured after 20 minutes at a wavelength of 480 mμ.

"Function" 4. The polyvinyl alcohol used in the present invention has an iodine absorbance of <0.5 to 0.5 as described above, whereas the iodine absorbance of the generally commercially available partially saponified polyvinyl alcohol is 0.2 to 0.4. It is a specific polyvinyl alcohol that exhibits an extremely high iodine absorbance of 8.

Such a high iodine absorbance is a value obtained by selectively using polyvinyl alcohol, in which acetic acid residues are formed more collectively along the polymer chain, among partially saponified polyvinyl alcohols.

If the iodine absorbance is less than 0.5, the effect of suppressing bubbles generated during dissolution in a hydrophilic liquid cannot be obtained, and the desired effect of the present invention cannot be achieved. However, if the iodine absorbance exceeds 0.8, the emulsifying ability decreases, so in the method of the present invention, polyvinyl alcohol having a specific iodine absorbance of 0.5 to 0.8 is selectively used. It is.

The above specific polyvinyl alcohol is -i, based on 100 parts by weight of the hydrophobic liquid encapsulated in the microcapsules.
It is desirable to dissolve it in the hydrophilic liquid in an amount of about 0.5 to 20 parts by weight, more preferably about 1 to 5 parts by weight.

Note that, if necessary, a conventional emulsion stabilizer as described above and a surfactant such as funnel oil, polyoxyethylene alkyl ether, or sorbitan fatty acid ester can be used in combination, but the amount used is determined according to the desired amount of the present invention. It is necessary to keep it within a range that does not impede the effects of

In the method of the present invention, examples of the polyvalent isocyanate used to encapsulate the hydrophobic core substance include m-phenylene diisocyanate, p-phenylene diisocyanate, 2.6-) lylene diisocyanate, 2.4-
Tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate , Xylyre saw 1.
4-diisocyanate, xylylene-1°3-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, ethyridine diisocyanate, cyclohexocyanate Silene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, isophorone diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethyridine diisothiocyanate, dimethylsilyl diisocyanate, vinylmethylsilyl Isocyanate, diisocyanate or diisothiocyanate such as 4-isocyanatemethyl-1,8-octamethylene diisocyanate, lysine diisocyanate, bis(isocyanatemethyl)cyclohexane, dicyclohexylmethane diisocyanate, trimethylhexamethylene diisocyanate, 4.4'.

4″-) liphenylmethane triisocyanate, toluene-2,4,6-) diisocyanate, tris(isocyanate phenyl) thiophosphate, methylsilyl triisocyanate, vinylsilyl triisocyanate,
Phenyldylyl triisocyanate, octadecylsilyl triisocyanate, methoxysilane triisocyanate, butoxysilane triisocyanate, octylsilane triisocyanate, 2,6-diitsyanate cabroic acid-β-isocyanate ethyl ester, 2,6
- diisocyanate caproic acid - γ-siicyanate propyl ester, 2,6-diisocyanate caproic acid -2-methyl-β-isocyanate ester, triisocyanates such as hexamethylene diisocyanate trimer, polymethylene polyphenylisocyanate, 4 ．．
4'-dimethyldiphenylmethane-2,2',5.5'
- polyvalent isocyanates such as uresotho-type polyisocyanates containing residues derived from tetraisocyanate, tetraisocyanate silane, hexamethylene diisocyanate and isophorone diisocyanate, and these polyvalent isocyanates in combination with polyvalent amines, polyvalent carboxylic acids, polyvalent Examples include those added to a compound having a hydrophilic group such as a valent thiol, a polyhydroxy compound, and an epoxy compound.

Examples of hydrophobic liquids include cottonseed oil, hydrogenated terphenyl, hydrogenated terphenyl derivatives, alkyl biphenyl,
Natural or synthetic hydrophobic liquids such as alkylnaphthalenes, diarylalkanes, kerosene, paraffins, naphthenic oils, and dibasic acid esters such as phthalic acid esters can be used alone or in combination.

The amount of the isocyanate compound added to the hydrophobic liquid is from 0.02 to 100 parts by weight of the hydrophobic liquid.
A range of 60 parts by weight is effective, more preferably 0.
The amount is adjusted within the range of 0.03 to 40 parts by weight.

Note that a polyvalent amine may be added to the hydrophilic liquid depending on the desired capsule quality. Any polyvalent amine can be used as long as it has two or more NH or NH2 groups in its molecule and can be dissolved or dispersed in the hydrophilic liquid forming a continuous layer. As a specific substance,
For example, aliphatic polyvalent amines such as diethylenetriamine, triethylenetetramine, 1°3-propylene diamine, hexamethylene diamine, etc., epoxy compound adducts of aliphatic polyvalent amines, alicyclic polyvalent amines such as piperazine, etc.;3. 9-bis-aminopropyl-2,4,8,10
Examples include heterocyclic diamines such as -tetraoxaspiro-[5°5]undecane.

The amount of these polyvalent amines added is appropriately determined depending on the type and amount of the polyvalent isocyanate used, the desired capsule wall strength, etc.
It is desirable to adjust the amount to 0.1 to 200 parts by weight, more preferably 1 to 100 parts by weight.

According to the method of the present invention, by selectively using polyvinyl alcohol having the specific iodine absorbance, the generation of bubbles when polyvinyl alcohol is dissolved in a hydrophilic liquid is effectively suppressed, and this generation is further suppressed. It will be done.

Therefore, efficient stirring of the system in the capsule manufacturing process becomes possible, and the occurrence of deposits on the reaction vessel is significantly reduced. Moreover, since the above-mentioned specific polyvinyl alcohol has a high emulsifying ability, the energy required for emulsifying the hydrophobic liquid is also saved.

The microcapsules produced by the method of the present invention are
Various pharmaceuticals, fragrances, dyes, pesticides, adhesives, liquid crystals, foods,
It is suitable for encapsulating solvents, rust preventives, toners, etc., and is particularly useful for applications such as printing inks and pressure-sensitive copying paper.

"Example" In order to more specifically explain the method of the present invention, examples relating to the production of microcapsules for pressure-sensitive copying paper will be described below, but the present invention is not limited thereto, of course. Note that parts and % in the examples indicate parts by weight and % by weight, respectively, unless otherwise specified.

Example 1 In a hydrophilic liquid consisting of 100 parts of a 3% aqueous solution of partially saponified polyvinyl alcohol (trade name PVA-217EE, manufactured by Kuraray Co., Ltd.) with an iodine absorbance of 0.58, diisopropylnaphthalene (trade name -113°, manufactured by Kureha Chemical Co., Ltd.) was added. 100 parts of crystal violet lactone, polymethylene polyphenylisocyanate (trade name Millionate MR)
400, manufactured by Nippon Polyurethane Industries Co., Ltd.) and 1 part of 2-isocyanatoethyl-2,6-dicyanatohexanoate (trade name T-100, manufactured by Toshi Co., Ltd.) were added to the hydrophobic liquid. It was emulsified and dispersed so that the average particle size was 6 μm.

In addition, the time required to obtain an average particle size of 6 μm at 9000 rpm using a homomixer (type M, manufactured by Tokushu Kikai Kagaku Kogyo Co., Ltd.) for T was described in the table as the emulsifying ability.

Next, 1 part of diethylenetriamine was added to the system, the temperature of the system was raised to 90° C., and the mixture was reacted for 3 hours while stirring to prepare a capsule dispersion.

There was almost no foaming during the reaction, and the apparent specific gravity of the capsule dispersion liquid 1 hour after the start of heating was 0.97.

A capsule dispersion liquid could be stably prepared without any deposits on the reaction vessel.

50 parts of starch particles were added to this capsule dispersion, diluted to a concentration of 20% to obtain a capsule coating liquid, and the resulting coating liquid was applied to a 40 g/g base paper using an air knife coater to reduce the solid content to 4. An upper paper was prepared by smearing the sample at a concentration of g/%.

[Creating the bottom sheet]

65 parts of aluminum hydroxide, 20 parts of zinc oxide, 3.5-
Mixture of zinc di(α-methylbenzyl)salicylate and α-methylstyrene/styrene copolymer (melt ratio 80/
20) Add 20 parts (solid content) of carboxy-modified styrene-butadiene copolymer Latinx to a dispersion obtained by grinding 15 parts of polyvinyl alcohol aqueous solution (solid content) and 300 parts of water in a ball mill for 24 hours. The prepared color developer coating liquid was smeared onto a 40 g/rrr base paper using an air knife coater so that the solid content was 5 g/rd to prepare a base paper.

When the upper paper was superimposed on the lower paper and printed using a typewriter, an extremely clear colored image was obtained. In addition, as a heat resistance evaluation test, the upper paper and the lower paper were stacked so that the coated sides faced each other, and treated in a heat treatment machine at 120°C for 3 hours under a load of 5 kg / ctM to evaluate the color development. The degree of coloration of the surface to which the agent is applied is measured using a Macbeth color densitometer (red filter).
) and are listed in the table. [The smaller the number, the better the heat resistance] Furthermore, as an evaluation test for scratch resistance, the upper paper and the lower paper were stacked so that the coated sides were facing each other, and 5 kg
The samples were rubbed together five times under a load of /-, and the degree of color staining on the surface coated with the coloring agent was determined, and the results are listed in the table.

◎: Almost no dirt.

○: Slightly dirty.

Comparative Example 1 Iodine absorbance is 0.38 as polyvinyl alcohol
Partially saponified polyvinyl alcohol (trade name: PVA-21)
A capsule dispersion was prepared in the same manner as in Example 1, except that 7, manufactured by Kuraray Co., Ltd.) was used.

There was significant foaming during the reaction, and the apparent specific gravity of the capsule dispersion liquid 1 hour after the start of heating was 0.40. A large amount of deposits were observed in the reaction vessel, and it was not possible to stably prepare a capsule dispersion.

In addition, similar to Example 1, various evaluation tests were conducted and the results are listed in the table.

Comparative Example 2 Iodine absorbance is 1.23 as polyvinyl alcohol
Partially saponified polyvinyl alcohol (trade name: PVA-42)
A capsule dispersion liquid was prepared in the same manner as in Example 1, except that the capsule dispersion liquid was used.

There was significant foaming during the reaction, and the apparent specific gravity of the capsule dispersion liquid 1 hour after the start of heating was 0.49. A large amount of deposits were observed in the reaction vessel, and it was not possible to continuously prepare a capsule dispersion without washing.

In addition, similar to Example 1, various evaluation tests were conducted and the results are listed in the table.

11LI - table

Claims (1)

[Claims] (1) Microcapsules in which a hydrophobic liquid containing polyvalent isocyanate is emulsified and dispersed in a hydrophilic liquid in which polyvinyl alcohol is dissolved, and a synthetic polymer film is formed at the droplet interface to cover the surface of the droplet. A method for producing microcapsules, characterized in that polyvinyl alcohol having an iodine absorbance defined below of 0.5 to 0.8 is used as the polyvinyl alcohol. [Iodine absorbance] 7 ml of water to 1 ml of 0.5% polyvinyl alcohol aqueous solution
2 ml of 0.001 N iodine aqueous solution (iodine:potash/1:2 weight ratio) was added dropwise and stirred, and the absorbance of the solution after 20 minutes was measured at wavelength 4.
Value obtained by measuring at 80 mμ.